Stabilization of Undercoordinated Cu Sites in Strontium Copper Oxides for Enhanced Formation of C2+ Products in Electrochemical CO2Reduction

Xiao Kun Lu, Bingzhang Lu, Haifeng Li, Khantey Lim, Linsey C. Seitz*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

The electrochemical CO2reduction reaction (ECO2RR) is a promising approach to generate renewable fuels and commodities with the integration of renewable energy. Cu-based catalysts produce an array of products resulting from the transfer of 2e-to 18e-during ECO2RR. Value-added C2+products are of great interest yet difficult to selectively produce. Oxide-derived Cu (OD-Cu)-type catalysts have shown improved selectivity and activity over metallic Cu catalysts that have not been preoxidized. Undercoordinated Cu sites on OD-Cu-type catalysts are suggested to be the active sites for enhanced C2+production. However, the stability of undercoordinated Cu sites remains largely unexplored in alkaline ECO2RR conditions. In this work, we prepare strontium copper oxide catalysts of varying Sr-Cu ratios and crystalline phases. We identify a SrCuO2tetragonal phase catalyst to be highly selective toward C2+products, exhibiting a 53% C2+Faradaic efficiency at -0.83 V vs reversible hydrogen electrode (RHE). Ex situ X-ray absorption spectroscopy (XAS) indicates that SrCuO2catalysts are able to retain or recover oxidized Cu species after exposure to reductive ECO2RR conditions for almost 1 hour, whereas OD-Cu remains in a metallic state. Furthermore, operando XAS of SrCuO2catalysts under alkaline ECO2RR conditions in a gas diffusion electrode-type flow cell reveals the formation and enhanced stabilization of Cu metallic moieties with a low coordination number of 6.3. This work suggests that tuning copper oxides via incorporation of secondary cations in the crystal lattice can further improve the stability of undercoordinated and higher-valence-state Cu sites for improved ECO2RR performance.

Original languageEnglish (US)
Pages (from-to)6663-6671
Number of pages9
JournalACS Catalysis
Volume12
Issue number11
DOIs
StatePublished - Jun 3 2022

Funding

This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This work made use of the EPIC facility and the Keck-II facility of the Northwestern University’s NUANCE Center, which have received support from the SHyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern’s MRSEC program (NSF DMR-1720139). This work made use of the IMSERC NMR facility at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), NSF CHE-1048773, and Northwestern University. This work made use of the Jerome B.Cohen X-ray Diffraction Facility supported by the MRSEC program of the National Science Foundation (DMR-1720139) at the Materials Research Center of Northwestern University and the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633).

Keywords

  • COreduction
  • alkaline electrolyte
  • gas diffusion electrode
  • low-coordinated Cu sites
  • operando XAS
  • oxide-derived Cu

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry

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